With confocal microscope apparatuses in the related art that generate three-dimensional images from a plurality of image slices, there is a known technology in which the dynamic range of the image slices is expanded by performing analog-to-digital conversion (AD conversion) of signals output from a camera after adjusting the signal levels so as to fall within a predetermined range by means of an automatic gain control (AGC) circuit (for example, see Patent Literature 1). With such a technology, image slices having good contrast can be obtained.